PARENT SESSION
Session #18: Mechanisms underlying the maintenance of diversity and mode of regeneration in tropical forests: tests of alternative hypotheses. Organized by: W.P. Carson, C. Gehring, and T. Theimer.
Wednesday, August 8, 2001. Madison Ballroom B
Inferring ecological organization from the phylogenetic structure of rain forest tree communities.
Webb, Campbell1, Donoghue, Michael1, 1
ABSTRACT- Much research into the maintenance of tropical tree diversity has focused on i) whether local communities are structured by niche differences, and ii) the role of antagonistic ecological interactions within and among species. The phylogenetic relationships of member species have seldom been addressed. However, since we expect a correlation between the phylogenetic relatedness of two taxa and their general ecological similarity (across many traits), measures of the overall phylogenetic relatedness of a community should inform us about the ecological similarity of member species. A null model of random community assembly from a species pool (at a larger spatial scale) can be used to assess whether observed assemblages of species are more or less phylogenetically related than expected. We may interpret higher-than-expected community relatedness (i.e., clumping of species on a phylogeny) to indicate spatial association of ecologically similar species, consistent with niche-driven habitat filtering. Conversely, lower-than-expected community relatedness indicates antagonistic interactions among ecologically similar species during local community assembly, consistent with interspecific competition. I found that tree species (≥10 cm DBH) in each of 28 plots (0.16 ha) in Bornean rain forest were more phylogenetically related than expected by chance, and inferred that variation in habitat among plots caused ecologically more similar species to co-occur within plots. These methods are a natural progression in the tradition of analyzing the taxonomic structure of communities (e.g., with species/genus ratios), and make use of the much stronger hypotheses of evolutionary relationships made possible by modern phylogenetic techniques. I will review the history of these ideas and suggest future directions in the study of community phylogenetic structure.
KEY WORDS: community assembly, phylogeny, Indonesian Borneo